Broadband Codecs for an Experimental 224 Mb/s PCM Terminal

High-speed PCM codecs (coders and decoders) have been constructed to handle broadband signals such as a mastergroup of telephone channels or an NTSC color TV signal. Two widely different approaches to the realization of the coding function are described. The first and earliest version utilizes a beam coding tube to convert the analog signal to digital form. The second approach employs a tandem array of solid-state stages to perform the required conversion. Associated circuits to implement the filtering, sampling, holding, timing, translation, framing, and decoding functions in a PCM codec are also described. Analysis results, experience gained in design, and measured performance of the coders and the associated circuits that make up a PCM codec demonstrate that they can be produced to meet stringent performance objectives.